Red X on slide thumbnails in Master View

The latest update to PowerPoint (not a Windows update) is supposed to fix or ameliorate the problem in several ways.

The problem, at least the one we all seem to be talking about in this thread, arises when some other program creates a lock on the PowerPoint file you're working on (or more specifically, the temp file that PowerPoint creates while you're editing the file).

This might be antivirus software, automatic backup software, file-synching software (OneDrive, etc) or anything else that monitors file changes and locks the file for any reason.

When PPT (pre-fix) tries to update the locked file, it can't;  worse, it can't *deal* with the situation properly and as a result, corrupts the presentation.

After the most recent update is applied, it tries several times to write to the locked file, giving the software that's holding the lock an opportunity to do whatever it's doing, and release the lock.  If the lock gets released, PPT can go on about its business, write to the file and all's well.

If the lock is never released for some reason, PPT can't write to it and will likely give messages about being unable to save, but should not corrupt the file, and should allow you to save it to a new name.

To learn whether you have the update that fixes (we hope!) these problems, go to File | Account and under Office Updates, check the Version.  It should be:  15.0.4615.1002

There's more about this specific update here:

http://support.microsoft.com/kb/2878315

Mostly, it says the same stuff that I've said above.  

If you don't have that update level, you'll want to enable updates and choose Update Now.

Note that the update cannot repair files that have already been damaged.  Once the unpatched version loses images and corrupts the file, the data's gone.  The patch *should* prevent the problem from recurring, however.

Steve,

What you are saying seems to make perfect sense.  While I have seen the problem working with documents from OneDrive and Dropbox, I have also seen the problem when working from a document that was attached to an email and not technically saved on my machine or one of my drives.  

I looked at my version of PowerPoint and it is 15.0.4615.1000. But when I download the update for the KB you reference I receive the message that the update is already installed.  So it looks like there might be a problem with MS version numbers or something else is going on.

Whether you can use a downloadable update or not may (I'm not positive of this, mind) depend on which edition of 2013 you have.  Can you post a screenshot of what you see in File | Account?

As Steve is hinting the update numbers are confusing. If you have the 64 bit msi installed version 15.0.4615.1000 is the updated version but it will usually also show 15.0.4613.1000!

I have version 15.0.4623.1000 and the problem just re-occurred today.

Ran an up-date, but the system says I am up-to-date.

Looks like MS hasn't yet fixed the problem......